Numerous types of earth supporting walls or structures such as bulkheads, quay walls, and seawalls have been used to divide a body of water from land. This invention is particularly applicable to bulkheads used as docks, but would apply to strengthening any wall. These supporting walls have been made of various materials, such as wood, metal and concrete. The bottom edge of such a supporting wall is driven or inserted into the earthen floor beneath the body of water. In situations where the water is relatively shallow and the wall fairly short, the driving of the bottom edge of the supporting wall into the earthen floor provides sufficient support for the wall to retain or hold back the ground from the water. However, where the water is deep and the wall is high, additional support for the wall is required. The usual method of providing additional support utilizes a tie rod connected at one of its ends to the wall and at its other end to a deadman. Another method of attaining the additional support is through the use of ground anchors inserted at an angle below horizontal through the wall and into the adjacent ground. The ground anchors are fixed in the ground and also secured to the wall. In either of these cases, the wall is designed to span between the rods and the soil below the water. Thus, the strength of the wall is a limiting factor on the design, as is the depth of the water.
U.S. Pat. No. 2,902,743 to King illustrates a method of constructing a concrete bulkhead. Additional support for the wall of the bulkhead is provided by a plurality of tie-rods or dead-men extending from the bulkhead to an anchor. U.S. Pat. No. 1,270,659 to Ravier illustrates a method of constructing original retaining walls. The retaining walls are constructed either of metal or concrete. Ground anchors are passed through pre-existing holes in the wall members to provide additional support for the wall during the original installation of the wall.
Ground anchors have been used to support retaining walls in various land construction situations, for example, at excavation sites. Such ground anchors are generally formed of rods or tendons received within holes in the ground and fixed to the ground by grout or concrete. The use of typical ground anchors in land construction situations is illustrated in U.S. Pat. No. 3,250,075 to Webb et al; U.S. Pat. No. 3,490,242 to Schnabel, Jr.; and U.S. Pat. No. 3,802,204 to Mason. In all of these cases, the ground anchors are installed from within the excavation, working close to the wall which is accessable.
Once a bulkhead wall is constructed, it determines the maximum depth of the harbor. This is because the wall is designed as a beam spanning between an upper row of rods and the soil below the harbor. Usually, to avoid major construction problems, the upper rods are placed at or near the level of water in the harbor. The other end of the wall is supported by the earth on the harbor side, and below the harbor (the toe support). The exact mechanism of this support is subject to some debate among engineers, but all parties agree that it is the only support for the bottom of the wall. The wall is constructed to provide earth access to deep water, so the earth acts against the wall and it must be designed to span between these two supports and resist the earth pressures on it. Usually, bulkheads are carefully designed for a known harbor depth.
When a dock or harbor is to be dredged, removal of the soil supporting the wall may cause it to fail. The failure may be caused by the wall displacing the remaining soil, or it may be because the span on the wall increased, and it is insufficient for the deeper harbor.
One prior art technique for deepening harbors, is to insert a new wall in front of the original wall, i.e., witin the water, and secure the new wall to the land with tie-rods. To attach the new wall to the tie-rods, the ground behind the original wall must be removed. The tie-rods must then be attached to the new wall and to an anchor located at a relatively large distance from the wall. However, such a repair technique is both time consuming and expensive.
The present invention was developed to provide a simple, less time consuming and less expensive technique for reinforcing existing bulkhead walls which separate a body of water from land. It is an object of the invention to allow the harbor to be dredged deeper and continue to safely use some existing bulkhead walls. The invention allows walls to be strengthened in a way that allows harbor dredging. It can also be used to strengthen any bulkhead wall. This is done by installing tie-rods below the harbor level through the wall.